Client Interfaces Guide > Introduction to Accessing Your Data through Client Interfaces > TDV Data Retrieval Tuning for Client Connections to TDV
 
TDV Data Retrieval Tuning for Client Connections to TDV
The way that data is retrieved from data sources and queued up in the TDV Server to provide data for your client applications can be tuned to optimize its retrieval. This method of retrieving data can approximate multithreaded data retrieval for client applications. This is especially beneficial for queries that return a large data set.
This feature improves the performance of queries by prefetching data from a data source and optimizing the data processing.
TDV can prefetch data for clients and store it on the TDV Server. The amount of data and the number of buffers used to store that data can be configured.
This tuning can be done using several TDV configuration parameters. The parameters work together to achieve results. Because each client application, query, and data source perform in different ways, it could take several attempts to determine the best settings for your exact circumstances.
 
Configuration Parameter
Description
DbChannel Prefetch Optimization
A boolean value that enables or disables this type of data retrieval tuning.
DbChannel Queue Size
An integer value between 0 and 100 that specifies the number of buffers that are allocated for prefetching data from a data source. It is recommended to use 10 as the starting value.
If you observe an increase in memory usage this parameter can be used to control the amount of memory used to prefetch data.
0: No queuing or prefetch of the results done on the server.
1 – 100:
• If prefetch optimization is enabled: This determines the max number of buffers a prefetch optimization can fill in on the server. The size of the buffer is determined by the fetchBytes, which can be set on the client. Default size of the fetchBytes is 128K.
• If prefetch optimization is disabled: Is always interpreted as 1 and the buffer size is the lesser of fetchBytes or fetchRows.
DbChannel Zigzag String Optimization
Zigzag strings, which can save bytes over the wire, will be used in client communications if requested by the client. This setting can be used to ignore the client setting.
If the setting is FALSE, the server will ignore the client setting, and the server will NOT send zigzag strings.
If the setting is TRUE, the client can request zigzagStrings to be sent across the wire.
It will not be necessary to restart server if this value changed.
It is recommended that this feature be turned on.
To tune data retrieval
1. Select Administration > Configuration from the Studio toolbar to open the Configuration panel.
2. Search for DBChannel.
3. Set DbChannel Queue Size to 10 (as a starting value).
4. Select Apply.
5. Set DbChannel Prefetch Optimization to true.
6. Select Apply.
7. Select OK to save changes and exit the Configuration dialog.
8. If necessary set the value of fetchBytes for your client interface.